This invention relates to a motor control system and more particularly, to a motor control system for use within a vehicle having an electric motor and which efficiently and accurately controls the torque provided by the motor, effective to satisfy the vehicle""s torque demands.
In order to reduce automotive emissions and the demand for fossil fuel, automotive vehicles have been designed which are powered by electric motors. Many of these vehicles use one or more sources of electrical power (e.g., fuel cells or batteries) to power an alternating current or xe2x80x9cACxe2x80x9d induction motor, such as a three-phase motor.
These types of vehicles reduce emissions and the demand for conventional fossil fuels by eliminating the internal combustion engine (e.g., in completely electric vehicles) or operating the engine at only its most efficient/preferred operating points (e.g., in hybrid electric vehicles). However, these types of vehicles suffer from some drawbacks. For example and without limitation, the conventional motor control systems and strategies used within these vehicles often do not consistently ensure that the torque requested by a driver operating the vehicle is accurately provided by the vehicle""s electric motor.
There is therefore a need for motor control system for use with an electric vehicle which substantially ensures that the torque requested by the driver of the vehicle is accurately provided by the vehicle""s electric motor.
It is a first object of the invention to provide a motor control system which overcomes at least some of the previously delineated drawbacks of prior motor control systems, strategies and methodologies.
It is a second object of the invention to provide a motor control system for use within a vehicle which substantially ensures that the motor of the vehicle accurately provides the driver-demanded torque.
It is a third object of the invention to provide a motor control system for use within a vehicle having a DC type power source and an AC type induction motor.
According to a first aspect of the present invention, a motor control system is provided for use within a vehicle including an alternating current type electric motor, a direct current type electrical power supply, and at least one driver-operated control. The control system includes a torque control portion which receives torque commands from the at least one driver-operated control and which is effective to provide a torque current and a flux current based upon said received torque commands; a vector control portion which receives the torque current and said flux current and which is effective to provide a first voltage value and a second voltage value based upon the torque current and said flux current; and a space vector pulse-width modulating portion, which is coupled to the power supply and to said motor, which receives the first voltage value and said second voltage value and which delivers a multi-phase voltage signal to the motor, effective to cause said motor to accurately deliver the torque commands.
According to a second aspect of the present invention, a method is provided for controlling an alternating current induction motor within a vehicle including direct current power supply, and at least one driver-operated control. The method includes the steps of receiving torque commands from the at least one driver-operated control; generating a torque current and a flux current based upon the received torque commands; generating a direct axis voltage and a quadrature axis voltage based upon the generated torque current and flux current; converting the direct axis voltage and the quadrature axis voltage into three-phase voltage pulse width modulated signal; and using the pulse width modulated signal and the direct current power supply to provide a three-phase voltage signal to the induction motor, effective to cause the induction motor to accurately deliver the torque commands.